Special Issue "Creep and Fracture of Engineering Materials and Structures"
Deadline for manuscript submissions: closed (30 April 2012)
Creep is time-dependent deformation under constant load or stress. It has been recognised as an engineering challenge for more than a century, and traditionally, the key design parameter has been ‘time to fracture’ as a function of applied stress and temperature. More recently, in applications, such as close-tolerance turbines and miniaturised equipment, ‘time to a critical strain’ has become a more appropriate failure criterion.
It is often regarded as a high temperature phenomenon, although this can be misleading since it is the homologous temperature (for metallic materials, this is the ratio of the current temperature to the melting temperature, expressed in degrees Kelvin) that is the salient factor in determining the significance of creep. Consequently, creep may still be a problem in solders for electronics at temperatures as low as −50 °C.
Creep may occur in all classes of materials (metals, ceramics, polymers and composites) although the phenomena involved are quite disparate. Even for a single material type, such as metals, one or more mechanisms may be involved, depending upon the operating conditions (stress, temperature, strain rate). For example, the dominant deformation process may be occurring at the grain boundaries or within the grains themselves. Further sub divisions are possible which explains the plethora of constitutive expressions for describing creep that have been developed over the years. With the advent of further miniaturisation and nanostructures, their number will undoubtedly mushroom, but the need to identify the dominant creep mechanism, both in the laboratory and in the field, will remain paramount, if reliable creep performance is to be achieved.
That this Special Issue contains a diverse range of papers should be regarded as strength. Potentially, there is much to gain from cross-fertilisation between different material-specific and application-specific approaches.Prof. Dr. Bill J. Plumbridge
- creep processes in materials
- failure criteria
- life prediction
- dominant mechanisms